The present invention relates to a composition comprising and methodology for using enzymes, as anti-infection agents, in the context of treating or lowering the risk of digestive tract infections.
In its 1998 Revision of the World Population Estimates and Projections, the United Nations Department of Economic and Social Affairs Population Division projected that the world population would reach 6 billion in 1999. The report also stated that it took only 12 years for the population to increase from 5 to 6 billion compared to 123 years to go from one to two billion. By the mid 21st century the projected population is between 7.3 and 10.7 billion. The remarkable population growth in the last decade is due partly to the efficient gains in food production resulting from the application of technology and intensive food production practices. For future growth, more efficiency gains in food production will be needed to keep pace.
One approach, which has made animal meat production more efficient, involves the widespread use of anti-microbial chemicals and antibiotics in animal feed. In large-scale farms, the spread of infection is very fast under the crowded production conditions. Widespread disease therefore is controlled by prophylactic and therapeutic uses of these substances. For example, it is common practice to incorporate chemicals in animal feeds to control coccidia infections (e.g., salinomycin, monensin, roxarsone (3-nitro), halquinol, carbadox and olaquindox) as well as anti-microbial antibiotics (e.g., bacitracin, virginiamycin, tylosin, tetracycline, chlortetracycline, penicillin, oleandomycin, novobiocin, lincomycin, bambermycins, apramycin, spiramycin, erythromycin, neomycin and others). This practice is well known to promote growth and improve feed conversion.
The rise in multiple antibiotic resistance among human pathogens, such as Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenza, Neisseria gonorrhoeae, and Mycobacterium tuberculosis, has created fear that antibiotic resistance developed in microbes associated with farm animals could be migrating to human pathogens through transferable drug resistance factors. There is evidence that animals fed with antibiotics are a source of bacteria with transferable resistance factors. See Hooge, Feedstuffs 71(20):59, 1999. Although the antibiotics used in animals and in humans are generally different, there are similarities in mechanisms that could result in cross-resistance. In one case, fluroquinolones are approved for control of E. coli infections (colibacillosis) in some animals and also are used in human medicine. Hooge, supra. Recently the FDA/CVM has proposed to withdraw the approval to use the fluroquinolone enrofloxacin in poultry due to the development of fluoroquinolone-resistant campylobacter and transfer to humans. See Murhead, S. Feedstuffs 72(45):1-4, 2000.
There also is a concern among meat-producing industries that yield loss and possible resurgence of animal disease could occur if there is a ban on use of antibiotics and antimicrobials in feed. In 1986, for example, Sweden banned the use of feed antibiotics and animal disease increased. This was accompanied by an increased use of therapeutic antibiotics that resulted in an overall increase in the use of antibiotics as well as increased meat animal production costs. See Smith, Feedstuffs 71(13):1, 1999. In December 1998, the EU Council of Ministers decided to suspend the use of six antimicrobials that were formally approved as prescription-free in feed growth promoters (Official Journal of the European Communities 29.12.98, Council Regulation No. 2821/98 concerning Directive 70/524). Two quinoxaline-based additives were also banned in August 1999 due to concern about residues in the meat. The result of these actions is an increased prevalence of conditions formally suppressed including: necrotic enteritis in broilers; enteritis due to Clostridium perfringens in weaned pigs; swine dysentery and spirochaetal diarrhoea; and E. coli-associated diarrhoea. See Miller, United States Animal Health Association, 1999 Proceedings xe2x80x9cAntibiotic Usages in Food Animal Production and Resistance-European Perspective.xe2x80x9d
There are 30,000 human deaths per year caused by nosocomial infections with resistant pathogens, but many fewer deaths from food borne pathogens. None of the deaths from food-borne pathogens have been linked to antibiotic resistance (see Smith, supra). Thus, it is not clear whether the use of antibiotics by the meat producing industries has contributed to the drug-resistant pathogen problem of the nosocomial infections in humans. Another concern is the lack of new antibiotics to treat infections with resistant pathogens. See Henry, C. M., Chemical and Engineering News, Mar. 6, 2000, pp 41-58. This could mean that when significant antibiotic resistant pathogens develop, there may be no new antibiotics available to treat the infections. The difficulty of developing antibiotics, market size, and regulatory issues seem to have caused the major pharmaceutical companies to move their RandD focus away from antibiotics development, especially for use in animals. New proposed regulations for registering a drug for animal use are so difficult that development is being stopped. See Smith, supra. There are, however, several small companies involved in the development of new antibiotics (Henry, supra).
In certain animal populations, infection is already pandemic. For example, avian coccidiosis is a disease that is only managed, but not really under control. Virtually all flocks are infected and anti-coccidiosis chemicals are commonly rotated in the feed to control damage and limit the development of resistant strains. Coccidiosis costs poultry producers $350 million annually in losses and medication expenses for antibiotic drugs such as salinomycin. See Suszkiw, USDA Agricultural Research Service News, Oct. 28, 1997. By 1999, it has been estimated that about $114 million would be spent annually on coccidiostats in the United States. See Frost and Sullivan, U.S. Pharmaceutical Products for Food Animals, Report 5245-54, 1995.
There is a clear need to find new and more effective methods to control infections in the digestive tract of animals that are grown using intensive farming practices. This need is based on a requirement to obtain better production efficiency in order to keep up with the rapidly expanding world population. Improved control of intestinal infection guarantees faster growth rate and improved feed efficiency. There is also a need for alternatives to antibiotic use in animal production to address the concern for possible antibiotic resistance development in human pathogens.
There is no risk of stimulating the evolution of resistant pathogenic microorganisms that present a problem for human health when using an enzyme-based treatment that operates in a manner different from all antibiotics. Since enzymes are proteins, there is no possibility that dangerous chemical residue will be incorporated in the meat products, as happens with some antibiotics and anti-coccidiosis chemicals. See American Feed Control Officials Inc., Official Publication, 1999, xe2x80x9cDrugs and Feed Additives, Section 30.0 Enzymes,xe2x80x9d pp. 206-217, ISBN 1-878341-10-3.
It is therefore an object of the present invention to provide an enzymatic treatment to reduce the impact of digestive tract infections.
It is another object of the present invention to provide a mechanism to reduce the impact of digestive tract infections by interfering with the binding of pathogens to the cells of the digestive tract.
It is yet another object of the invention to provide an approach for increasing weight gain and feed conversion with respect to animals that are infected with pathogens which cause infections or necrotic enteritis.
It is a further object of the present invention to provide a dosage form, suitable for oral administration that is effective in improving the condition of a subject infected by or at risk of infection by a microbial pathogen.
In accomplishing these and other objects, there has also been provided, in accordance with one aspect of the present invention, a composition comprising (i) an enzyme that cleaves a linkage that effects release of a cell-surface protein or carbohydrate, the enzyme being other than an endo-1,4-D-mannanase, and (ii) a physiologically acceptable carrier for the enzyme, wherein the composition is in a form suitable for oral administration and contains no anti-infection agent other than the enzyme. In one embodiment, the enzyme in question cleaves a linkage that effects release of a cell-surface protein.
In a preferred embodiment, the enzyme included in the composition is a sphingomyelinase or a phospholipase, especially a type C or a type D phospholipase. In another preferred embodiment, the enzyme is selected from the group consisting of esterases, cerebrosidases, and carbohydrases that cleave a linkage that effects release of a cell-surface protein or carbohydrate. In another embodiment, the enzyme is prepared from a Bacillus cereus strain, preferably ATCC 7004 or ATCC 6464. Alternatively, the enzyme is obtained by expressing the recombinant DNA coding for the enzyme in Bacillus megaterium. In another embodiment, the enzyme is contained in a gelatin capsule shell and is present in the composition at 200 IU/Kg-4000 IU/Kg feed.
In accordance with another aspect of the present invention, a composition has been provided, having the aforementioned constituents (i) and (ii), wherein the physiologically acceptable carrier is a foodstuff into which the enzyme is incorporated. Thus, the composition can be an animal feed that contains no other anti-infection agent other than the enzyme. The animal feed composition of the present invention further comprises grain material, such as corn, sorghum, wheat, barley or oats, a source of protein, such as beans or peas, and vitamins, amino acids, and minerals.
In accordance with yet another of its aspects, the present invention provides a composition, as described above, that is in a solid or a liquid dosage form.
There is further provided a method of treating or ameliorating the risk of a digestive tract infection, comprising orally administering, to a subject suffering from or at risk for suffering the infection, an effective amount of enzyme that cleaves a linkage that effects release of a cell-surface protein or carbohydrate, wherein the enzyme is other than an endo-1,4-D-mannanase. In addition, the method does not include administering an anti-infection agent other than the enzyme itself. The infection may be affected by a protozoan, such as Eimeria and Cryptosporidium, bacterial, such as Clostridium, fungal or yeast pathogen.
There is even further provided a composition comprising (i) an enzyme that cleaves a linkage that effects release of a cell-surface protein or carbohydrate and (ii) a physiologically acceptable carrier for the enzyme, wherein the composition is in a form suitable for oral administration and does not contain an anti-infection agent other than the enzyme.
The is also further provided a method of treating or ameliorating the risk of a digestive tract infection, comprising orally administering, to a subject suffering from or at risk for suffering the infection, an effective amount of enzyme that cleaves a linkage that effects release of a cell-surface protein or carbohydrate, wherein the method does not include administering, with the enzyme, an antimicrobially effective amount of another anti-infection agent.
Other objects, features and advantages of the present invention will become apparent from the following detailed description. The detailed description and specific examples, while indicating preferred embodiments, are given for illustration only since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. Further, the examples demonstrate the principle of the invention and cannot be expected to specifically illustrate the application of this invention to all the examples of infections where it will be obviously useful to those skilled in the prior art.